1a. Objectives (from AD-416):
The contribution of dietary oxidized fats to total energy intake has markedly increased with the higher inclusion rates of corn co-products and various other supplemental fat sources, which may cause suboptimal pig performance and negatively affect intestinal health. Only recently, have data been published on the impact of fat rancidity (oxidation) on fat digestibility and pig growth performance. However, no data are available on the impact of dietary oxidized fat on digestible and metabolizable energy (DE and ME, respectively) content, nitrogen retention, or its impact on oxidative stress and intestinal barrier function in growing pigs. Thus, there is a critical need to understand the impact of fat type and oxidation level on dietary energy (DE and ME) and nitrogen utilization, as well as its intestinal and physiological effects. There are limited data suggesting that feeding oxidized fat to swine increases oxidative stress, but the impact of dietary oxidized fat on intestinal barrier function and mucosal immunity is unknown. Therefore, the objectives of the proposed research are to: 1) Determine the variation in DE and ME content of 4 dietary fat sources ranging from saturated animal fat (tallow and poultry fat) and 2 unsaturated vegetable oils containing either low or high amounts of linoleic acid (canola and corn oil, respectively); 2) Determine the impact of lipid oxidation on DE and ME content and nitrogen retention; and 3) Determine the impact of dietary fat source and lipid oxidation on indicators of oxidative stress and intestinal barrier function.

1b. Approach (from AD-416):
Objective 1: Impact of lipid type and oxidation level on digestible (DE) and metabolizable (ME) energy. In addition to a control diet, 4 different lipid sources will be used in combination with 3 levels of oxidation (no oxidation, slow oxidation, rapid oxidation) to measure the impact of lipid type and oxidation on De and ME concentration. Pigs will be allowed to adapt to the experimental diets for 28 days, group-housed in pens (2 pigs/pen) which contain a self feeder and nipple waterer. After the 28-day diet adaptation period, pigs will be moved to individual metabolism crates designed for total, but separate, collection of feces and urine. Pigs will be allowed to adapt to the metabolism crates and feeding regimen (fed twice daily) for 3 days, following which a 4-day total urine and fecal collection period will occur. Pigs will be fed their respective experimental diets twice daily at an amount equivalent to approximately 4% of their body weight, and will be provided ad libitum access to water at all times. The nutrient balance experiment consists of utilizing 108 barrows weighing approximately 40 kg (body weight after the 28-day adaptation period), randomly assigned to one of 13 dietary treatments. The basal diet will be formulated to satisfy the nutrient requirements with test diets consisting of supplementing 10% of each lipid x oxidation combination on top of the basal diet. The difference method will be used to determine DE and ME content of each lipid source.
Objective 2: Impact of lipid type and oxidation level on excretion of secondary oxidation products. At the end of the 4-day collection period described above, all pigs will be fasted for 24 hours and urine will be collected to determine the concentration of polar and non-polar secondary oxidation products. Urine 4-HNE concentrations normalized to urine creatinine concentrations, and serum concentrations of TBARS will be measured as indicators of oxidative stress.
Objective 3: Impact of lipid type and oxidation level on intestinal permeability. On the final day of the experiment for Objective 2, the impact of dietary fat source and oxidation level on intestinal barrier function will be determined by administering an oral dose of a cocktail containing 10 grams of lactulose and 2 grams of mannitol to all pigs. Urine will be collected for a period of 6 hours following this feeding into a container with chlorhexidine to prevent microbial contamination. Urinary concentrations of lactulose and mannitol will be determined by HPLC, and the lactulose:mannitol ratio will be calculated as an indicator of small intestinal permeability. Blood samples will be collected from each pig following this feeding period (1 hour post-feeding), and serum concentrations of endotoxin will be determined as another indicator of intestinal barrier function. Blood samples will be collected after an overnight fast and at 3 hours after feeding for determination of endotoxin in both the fasted and fed state as indicators of systemic inflammation. Fecal concentrations of IgA will be determined on freshly collected and frozen fecal samples as a marker of mucosal immunity.

3. Progress Report:
Corn oil, canola oil, tallow, and poultry fat were obtained and peroxidized by a slow or rapid method and subsequently characterized by various analytical methods. Once peroxidized and characterized, pigs were then fed diets containing these lipids with measures of gut barrier function, serum immunity, and energy and nutrient digestibility were obtained. Animal experimentation has been completed and the data analyzed with manuscripts currently being written.
The data indicate that lipid peroxidation had no effect on gut barrier function or serum immunity, or on the digestible or metabolizable energy values for any of the lipids tested, and did not appreciably affect total tract digestibility of dietary dry matter, lipid, nitrogen, or carbon.